Wavelength Assignment In WDM Networks Research Articles

A Survey of Minimum Wavelength Conversion Routing and Wavelength Assignment in WDM Networks

Generally, research on routing and wavelength task over wavelength directed WDM networks is worried about immediate reservation (IR) requests. An IR demand typically does not specify a holding time for data transmission and the start time of the data transmission are assumed to be immediate (i.e. when the connection request arrives). The idea of advance reservation (AR) has as of recently been picking up consideration for optical networks. An AR request commonly determines data about the beginning of the information transmission or a cutoff time, just as the holding time of the transmission. AR has a few significant applications for both wide-region networks and Grid networks. For instance, AR can be utilized for modifying virtual geographies to adjust to predictable peak hour traffic use. It very well may be utilized to give high- bandwidth transmission administrations, for example, video conferencing and in Grid applications requiring the booked circulation of enormous records and for co-allotment of organization and grid assets. AR can likewise be advantageous to the organization by permitting the organization administrator to more readily design asset use and accordingly increment use. Information on the holding time can prompt more ideal choices for asset distribution. This translates to better quality of service for users. In this paper we give a complete study of the past and current work on booking ahead of time for optical organizations. There have been numerous varieties of the advance reservation of time idea proposed, so we will likewise give an expansive grouping. Notwithstanding the review, we will examine what we accept are significant regions of future work and open difficulties for early booking on optical organizations. Keywords: Advance reservation, scheduled demands, WDM, survey, wavelength-routed, and RWA

An Optimized Algorithm for Dynamic Routing and Wavelength Assignment in WDM Networks with Sparse Wavelength Conversion

An Optimized Algorithm for Dynamic Routing and Wavelength Assignment in WDM Networks with Sparse Wavelength Conversion

A load balanced approach of multicast routing and wavelength assignment in WDM networks

Multicast routing and wavelength assignment MRWA deals with the problem of one-to-many communication in a wavelength division multiplexed optical fibre networks. As physical optical networks are equipped with finite number of optical channels in each fibre cable, throughput of the network is treated as a major performance issue. The aim of this work is to maximise throughput in a finite wavelength WDM network. As to establish multicast session a single message may need to split into multiple messages fanning out of a node, the node must contain costly splitters. This work also considers the cost of splitting at the split nodes while establishing a light-tree for a particular multicast session request. Here a load-balancing technique is used to optimise the optical channel requirements to establish a multicast connection. The algorithm proposed here is compared with standard all-shortest path algorithm combined with first-fit wavelength assignment for multicasting by simulation on various network topologies and different network configurations. The simulation result shows that our proposed algorithm performs much better than the standard one.

Light Path Optimization Implementation for Survivable Routing and Wavelength Assignment in Optical Networks

In this paper, establishing a light path setup in WDM network done by implementing an ant-based mechanism Ant Colony Optimization (ACO) algorithm used for providing survivable routing in WDM network. The major problem in survivable routing WDM network is routing wavelength and assignment (RWA) problem, It sets up light path by routing and assigning a wavelength to each connection such that no light path use the same wavelength on same link .Our study aims to develop an routing and optimize the light path setup for survivable routing based upon the bit transmission to which supports data transfer supports to run continuously thus it can provide dynamic path. By adopting a new routing table structure and keeping a number of mobile agents in the network to cooperatively explore the network states and continuously update the routing tables, our new ant algorithm can efficiently support the ants' foraging tasks of route selection and wavelength assignment in WDM networks. Each path in the network is assigned by feasibility value. This feasibility value is calculated by considering the metrics such as bandwidth availability, path length and number of free wavelengths. When an ant is launched in the network by its node, it moves towards random destination to gather information such as bandwidth availability, path length and free wavelengths in that path. The value of path load is dynamically updated by the mobile agents in the load table. Using NS-2 simulation we show that the proposed ant based routing achieves better channel utilization and throughput with reduced delay, when compared with the normal routing. Optimization of light path performance is measured by varying the CBR traffic sending rate and flows.

Ant colony optimization for dynamic routing and wavelength assignment in WDM networks with sparse wavelength conversion

Since optical WDM networks are becoming one of the alternatives for building up backbones, dynamic routing, and wavelength assignment with delay constraints (DRWA-DC) in WDM networks with sparse wavelength conversions is important for a communication model to route requests subject to delay bounds. Since the NP-hard minimum Steiner tree problem can be reduced to the DRWA-DC problem, it is very unlikely to derive optimal solutions in a reasonable time for the DRWA-DC problem. In this paper, we circumvent to apply a meta-heuristic based upon the ant colony optimization (ACO) approach to produce approximate solutions in a timely manner. In the literature, the ACO approach has been successfully applied to several well-known combinatorial optimization problems whose solutions might be in the form of paths on the associated graphs. The ACO algorithm proposed in this paper incorporates several new features so as to select wavelength links for which the communication cost and the transmission delay of routing the request can be minimized as much as possible subject to the specified delay bound. Computational experiments are designed and conducted to study the performance of the proposed algorithm. Comparing with the optimal solutions found by an ILP formulation, numerical results evince that the ACO algorithm is effective and robust in providing quality approximate solutions to the DRWA-DC problem.

On-Line Optimal Wavelength Assignment in WDM Networks With Shared Wavelength Converter Pool

In this paper, we study on-line wavelength assignment in wavelength-routed WDM networks under both unicast and multicast traffic where nodes in the networks have wavelength conversion ability. Since wavelength converters are still expensive and difficult to implement, we consider the case where nodes in networks have only a limited number of converters that are shared by all input channels. We study the problem of setting up connections in such networks using minimum number of wavelength converters. For unicast traffic, we first study the problem of setting up a lightpath on a given link-path with minimum number of conversions. We give a simple algorithm that solves it in O(tk) time where t is the number of links on the path and k is the number of wavelengths per fiber, as compared to the best known existing method that needs to construct an auxiliary graph and apply the Dijkstra's algorithm. We also consider the problem of setting up a lightpath while using wavelength converters at nodes with fewer available converters only when necessary, and give an O(tk) time algorithm. We then generalize this technique to WDM networks with arbitrary topologies and give an algorithm that sets up an optimal lightpath network-wide in O(Nk+Lk) time, where N and L are the number of nodes and links in the network, respectively. We also consider multicast traffic in this paper. Finding an optimal multicast light-tree is known to be NP-hard and is usually solved by first finding a link-tree then finding a light-tree on the link-tree. Finding an optimal link-tree is also NP-hard and has been extensively studied. Thus, we focus on the second problem which is to set up a light-tree on a given link-tree with minimum number of conversions. We propose a new multicast conversion model with which the output of the wavelength converter is split-table to save the usage of converters. We show that under this model the problem of setting up an optimal light-tree is NP-hard and then give efficient heuristics to solve it approximately

Converter-Aware Wavelength Assignment in WDM Networks with Limited-Range Conversion Capability

In wavelength-routed optical networks, wavelength converters are considered as one of the most critical network resources because they can significantly reduce the blocking probability, but still remain quite expensive. Unfortunately, previous wavelength assignment algorithms have seldom considered their presence. Therefore, in this paper, we propose a novel dynamic algorithm that can minimize the number of wavelength translations. Our algorithm establishes lightpaths by connecting a minimum number of wavelength-continuous segments. We mathematically prove the correctness of our algorithm. Then, we carry out extensive performance evaluations over three typical topologies with full-range or limited-range converters to compare our proposed algorithm with first-fit and most-used algorithms. The simulations show that, to obtain similar blocking performance, our algorithm requires much fewer converters, or the same number of converters but with smaller conversion ranges. From another perspective, with the same conversion capacity, our algorithm can significantly improve the blocking performance. Our algorithm is also scalable due to its polynomial time complexity and insignificant local signaling overhead.

Multicast routing and wavelength assignment in WDM networks: a bin packing approach

We address the problem of multicast routing and wavelength assignment (MClowbarRWA) in wavelength-routed WDM optical networks. Multicast requests are facilitated in WDM networks by setting up so-called light trees and assigning wavelengths to them. Objectives of the MClowbarRWA problem include minimizing the number of distinct wavelengths used to establish a set of multicast requests and minimizing the cost of the corresponding light trees. This cost can represent the physical length, delay, or actual cost of a tree. Applications that require quality of service (QoS) multicasting can impose additional constraints on light trees, such as a bounded end-to-end delay. Proposed are heuristic algorithms based on bin packing methods for the general MClowbarRWA problem, which is NP complete. These algorithms can consider unicast, multicast, and broadcast requests with or without QoS demands. Computational tests indicate that these algorithms are efficient, particularly for dense networks.

Efficient heuristic algorithms for light-path routing and wavelength assignment in WDM networks under dynamically varying loads

This paper presents heuristic algorithms that may be used for light-path routing and wavelength assignment in optical WDM networks under dynamically varying traffic conditions. We consider both the situations where the wavelength continuity constraint is enforced or not enforced along a light-path. The performance of these algorithms has been studied through simulations. We also compare their performance with that of a simpler system that uses fixed shortest-path routing. Our proposed algorithms provide lower blocking probabilities and are simple enough to be applied for real time network control and management. The heuristic algorithms are computationally simple and efficient to implement and provide good wavelength utilisation leading to efficient usage of the network's resources.

Backtrack routing and priority-based wavelength assignment in WDM networks

In this paper, we consider two key problems in the WDM networks: the wavelengh assignment and routing problems. The objective of the problems is to minimize the request blocking rate. We propose two priority-based methods for the wavelength assignment problem: static and dynamic strategies. Based on the priority of an incoming request, the proposed methods allocate a wavelength among the available wavelengths for the given priority. Analytic models and simulations are presented for the proposed wavelength assignment methods so as to analyse the link blocking rate. The simulation results show that the link blocking rate by the dynamic strategy is less than that by the assignment strategy. We also develop a routing algorithm that works together with the proposed wavelength assignment methods to reduce the overall blocking rates. The proposed routing method maintains a routing tree for a given connection request. Based on the routing tree, the algorithm finds a route with one available wavelength for each link along the route. We compare the proposed routing method with the fixed routing and fixed alternate routing algorithms. The experiments show that the proposed routing algorithm performs better than the fixed routing and the alternate routing methods.